Cellular flotation structure

ABSTRACT

A cellular flotation structure made up of identical regular rhombododecahedra packed without voids between them to provide a structure with greater strength and uplift when submerged. The structure is suitably made up from moulded panels which each define a plurality of semi-cells, in the form of semirhombododecahedra, and are aligned and joined together. Marginal cells can be reinforced.

United States Patent 11 1 Maistre CELLULAR FLOTATION STRUCTURE [76] Inventor: Michel Antoine Jules Maistre, 19

rue dAusterlitz, 33 Bordeaux-Cauderan, France [22] Filed: -Mar. 17,1972 [21] Appl. No.: 235,537

[30] Foreign Application Priority Data Mar. 18, 1971 [52] US. Cl. 114/16 R,-114/.5 F, 161/68,

161/137, 52/81, 52/DlG. 10, 52/237 [51] Int. Cl. 363g 8/04 [5 8] Field of Search 161/68, 69 127,133-137;

, 52/81, 237, DIG. 10; 114/.5 F, 43.5, 16 R [56] References Cited:

I v UNITED STATES PATENTS 3,632,109 11197 0611116642... 52/1310. 10

France 71.09587 [in 3,842,768 1451 1 Oct. 22, 1974 3,663,347 5/1972 Scho en .Q. 52/1210. 10

3,665,882 5/1972 Georgiev et a]. 52/DlG. l0

' OTHER PUBLICATIONS Critchlow, K., Order 111 Space, Thames and l-ludson,

,London,.(1971), Appendix 2.

Cundy, 11. M. and A. P. Rollett, Mathematical M611"- els, Oxford University Press, 1961, pp. 120, 145.

Primary ExaminreGeorge F. Lesmes Assistant Examiner stanley S Silverman gether. Marginal cells can bereinforced.

13 Claims, 13 Drawing Figures PATENTEBUCTZZIBM sum 20? 7 'Pmamenwzz 3, 842. 768

SHEET GDP 7 FEW? nd lgl l CELLULAR FLOTATION STRUCTURE The present invention relates to a cellularflotation structure.

The structure of the invention is particularly butnot exclusively adapted to resist very high hydrostatic pres sures, and to be used as a flotation volume when immersed at depth.

In the field of submarine applications, there is a need for leak-tight flotation structures of density less than unity, in order to compensate for the weight in water of materials of density greater than unity.

Both natural products, such as cork or balsa, or syn.-' thetic materials, such as synthetic foams or composite materials consisting of hollow spheres embedded in' a continuous matrix material,*have already been used for this purpose.

The natural products do not have sufficient strength for use other than in shallow immersions.

The synthetic foams comprise great numbers of cells of small dimensions, the shapes-and distributions of which are irregular, so that the resistance of the foams to hydrostatic pressure is limited.

The synthetic composites generally comprise cells in the shape of hollow spheres filling an envelope, either micro-spheres packed loosely, in a random arrangement in a filler matrix or macro-spheres arranged in a regular manner in the matrix to provide an arrangement of a maximum compactness.

The composites including micro-spheres are subject to very variable stresses from one point to another as a result of imperfections in the actual geometry of the micro-spheres and as a result of their disordered stack mg.

The composites comprising macro-spheres require'a matrix material which represents at least 26 percent of the total volume of the composite, and, in practice, serves only to give cohesion between the macrospheres and to transmit the hydrostatic pressure around each of the macro-spheres. Thus, in practice, this matrix material does not contribute towards increasing the resistance to implosion of the cells, and it merely forms an inert mass.

Thus, the imperfections of these known composites lead to relatively low implosion pressures relative to their density, having regard to the intrinsic properties of the materials of which theyare formed.

According to the present invention there is provided a cellular flotation structure including at least two su-' perposed layers of juxtaposed watertight cells, the cells being identical regular rhombododecahedra arranged face to face without voids between them.

Preferably the cells are each formed by joining two semi-cells in the form of semi-rhombododecahedra along their free edges, the edges lying in a median plane of the formed cell. a

In preferred embodiments the structures consist of a plurality of panels, each panel defining at least one layer of semi-cells in the form of semirhombododecahedra and forming, with asimilaradjacent panel to which it is attached, a layer of complete cells in the form of rhombododecahedra.

Suitably, at least the interior panels of the structure each define two layers of semi-cells in the form of semirhombododecahedra, each wall of each semi-cell being common to another semi-cell and some semi-cells open on each of two parallel faces of the interior panels.

A rhombododecahedron has l2 faces each in the form of a rhombus, i.e., diamond shaped, and 24 edges and 14 corners. At six of the corners four edges meet, and at each of the other eight corners three edges meet. In this specification, the corners are referred to as four edge corners or three edge corners appropriately.

The cells are stacked so that the plane walls of one cell of rhombododecahedral shape are juxtaposed to one of the plane walls of (in this case of an interior cell) the 12 neighbouring cells, and the cells adhere firmly to each of'the neighbouring cells by one of their walls. Each cell in the shape of a regular rhombododecahe- 1 dron has the property of being able to be stacked so as to occupy the whole of theavailable space, so that each of the 12 faces or walls of a cell of this shape matches up perfectly with a face of each of the twelve neighbouring cells. The structure thus consists essentially of a three-dimensional network of plane walls, in the shape of diamonds, each marking the boundary of two adjacent cells. Under the effect of the hydrostatic pressure, each of its walls is subjected to a plane compression stress, oriented according to its own direction, and the level of these stresses is the same for all the walls of which the structureconsists, sothat the whole of the material is placed under stress in a completely homogeused to the best possibleadneous manner and "is thus vantage.

The side walls of the structure forming a volume maybe reinforced. in effect, the walls defining the marginal cells and the-exterior of thestructure are further subjected to bending stresses resulting from the pressure difference between the interior of the cells and the hydrostatic pressure of the ambient medium. -ln

order to allow them to offer resistance to these additional stresses, these walls are reinforced so that they cannot constitute a point of least resistance for the whole of the flotation structure. This reinforcement is produced either by increasing their thickness, or by coating the marginal cell walls with a rigid material, or by filling'all the marginal cells with a rigid material] The half-cells are joined by moulding and gluing together in a leak-tight manner, two by two, along the edges surrounding their apertures in such a way as 'to form a hermetically sealed rhombododecahedral cell.

The panels are assembled in pairs and by gluing, so that the edges defining the apertures of the cells of one panel coincide exactly with the edges of the apertures of the cells of another panel. The pairs of panels are assembled by gluing to other pairs of elementary panels,

so that a wall of a cell belonging to one'pair of panels coincides with and'is joined to a wall of the same slope of a cell belonging to the other pair of panels.

The panels comprise half-cells, those apertures .of which open on-the same'faceare adjacent and sepa-. rated from one another only by the thickness of the walls defining the cells. I I j Suitably, the thickness of the interiorpanels is equal to the height of the semi-rhombododecahedra-in the direction ofpanelthickness between the said parallel faces. 7

In one form, each of the said two parallel faces of the interior panels includes apertures of some semi-cells and interior corners of the semi-cells which open in the other said parallel face;

In another form, ,each of the said two parallel faces of the interior panels includes apertures of some semiflotation cells and inner bottom walls of the semi-cells which open in the other parallel face.

Alternatively-each of the said two parallel faces of the interior panels includes apertures of some semicells, which are formed by walls perpendicular to the parallel face and terminating at the parallel face, and by inclined inner walls which are also inner walls of the semi-cells having apertures in the other parallel face. The exterior panels of the structure may comprise exclusively half-cells which open towards the middle of the flotation structure, whilst the outer side comprises a plane face consisting of a covering or coating layer, preferably of the same nature as that forming the walls of the semi-cells.

In order that the'invention may be more clearly understood, the following description is given, merely by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a regular rhombododecahedron. Shown cross hatched is a central cross-sectional plane including the mid point of the body and perpendicular to a straight line passing through the mid point and through two opposite four edge corners of the rhombododecahedron;

FIG. 2 is a perspective view of a part of an elementary panel comprising half rhombododecahedra, each cut along the plane shown in FIG. 1 and opening up wards; 7

FIG. 3 is a perpendicular cross-section of two superimposed elementary panels comprising half rhombododecahedra which are connected to form whole rhombododecahedral cells, the half-cells of thelower layer being cut along the plane S of FIG. 2;

FIG. 4 is a perspective view of three elementary'panels of rhombododecahedral half-cells of which some open upwards and some open downwards, the panels comprising walls belonging simultaneously to upwardly and downwardly opening half-cells, the plane of vertical cross-section of the half-cells shown passing through the plane defined by corners CDI of a half-cell of FIG. 2;

FIG. 5 is another perspective view of a regular rhombododecahedron. Shown cross hatched is a crosssectional plane through the mid point and perpendicular to a straight line passing through the mid point and through the two opposite three edge corners;

FIG. 6 is a perspective view of two elementary panels each comprising a plurality of half rhombododecahedra, each cut along the plane of FIG. 5, the elementary panels being adapted to be superimposed so that opposite pairs of half-cells are joined to form whole regular rhombododecahedral cells;

FIG. 7 is a perspective view of a single half-cell opening on the upper face of an elementary panel with its closed bottom back to back with the closed upper end walls of the half-cells which open on the lower face of the same elementary panel, the half-cells being cut on the plane of FIG. 5;

FIG. 8 is a perspective view of three elementary panels each with a double layer of rhombododecahedral half-cells cut in the plane of FIG. 5, some opening upwards and the others opening downwards, the panel having interior walls each belonging to an upwardly and a downwardly opening half-cell, and also walls common to half-cells opening in the same direction;

FIG. 9 is another perspective view of a regular rhombododecahedron. Shown cross hatched is a crosssectional plane through the mid point and perpendicular to a straight line passing through the mid point of the dodecahedron and'the centre of two parallel faces of the said dodecahedron;

FIG. 10 is a perspective view of an elementary panel of half-cells of rhombododecahdral shape in which the half-cells are cut along the plane shown in FIG. 9, and are alternately open towards the top and towards the bottom of the panel;

FIG. 11 is a perspective view of two superimposed elementary panels of half-cells of rhombododecahedral shape which are cut-along the plane of FIG. 9 and can be superimposed so as to form whole rhombododecahedral cells;

FIG. 12 is a perspective view of the corner of an elementary panel of a double layer of half-cells according to FIGS. 7 and 8 in which the peripheral or outer halfcells are filled with a rigid packing material; and

FIG. 13 is a perspective view of three elementary panels, of which the central panel is a double layer of half-cells each out along the plane of FIGS, and the upper and lower panels comprising a single such layer, the panels being superimposabl'e to form'a flotation volume with two layers of complete rhombododecahedral cells with external walls reinforced by a coating.

In FIGS. 1, 5 and 9, are shown regular rhombododecahedra ofwhich the six four edge corners A,

B, C, D, E and F lie on a sphere (of radius R) and of which the eight three edge corners G to N lie on a sphere of radius r R V372. The rhombododecahedra comprise twelve identical diamond-shaped faces; and the edges of the faces, for example AKDL, measure R \/372 and the two diagonals of each face are R and R \/2 respectively. The plane faces are at angles of to'the planes of adjacent faces.

The rhombododecahedra are each shown with a cross-sectional median plane which passes through the centre and is perpendicular to a line passing through the centre. In the case of FIG. 1 the line joins two four edge corners A and B; in the case of FIG. 5 the line joins two three edge corners H and I and in the case of FIG. 9 the line joins the centres of two opposite parallel faces. The semi-rhombododecahedra or semicells formed on cutting the bodies of FIGS. 1, 5 and 9 on the illustrated planes, can be produced by moulding a preferably synthetic material in moulds of suitable shape. The semi-cells can thereafter be combined in pairs, for example by gluing, so as to form complete leak-proof cells of rhombododecahedral shape. For a structure of the invention, the thickness of the walls is preferably of the order of one fifth to'one tenth of the radius R of the sphere circumscribing the rhombododecahedron. In order to produce a cellular flotation structure, each rhombododecahedral chamber is coated with a binder or a glue and is placed beside another chamber, so that each diamond-shapedface of one of the chambers coincides exactly withone face of another chamber.

In order to simplify the manufacture of the cellular flotation structure, it is proposed according to the invention, to make it up from several elementary panels each comprising'a series of juxtaposed and if necessary superimposed half-cells. The apertures of the half-cells can open either only on one side or on both sides of each elementary panel.

If half cells formed by cutting a rhombododecahedron on the plane of FIG. 1 are used, then these can be formed into an elementary panel as shown in FIG. 2,

the apertures such as CDEF of each half-cell 1 consisting of a square and opening on both sides of this panel. In FIG. 3 there is shown a cross-section of two such elementary panels 1, 2 of half-cells, this view being a cross-section perpendicular to the diagonals CF and DE and passing through the top B of a half-cell according to FIG. 2. The lower elementary panel 1 is covered by the upper elementary panel 2 which in turn comprises several half-cells which are symmetrical to those of the upper elementary panel. Thus, in this FIG. 3, of the corners A, B, E, F, G, H, J, L, M and N of a whole cell like that of FIG. 1 of rhombododecahedral shape are seen. The edges surrounding the apertures of the half-cells opening upwards in the lower panel 1 are glued in a suitable manner against the corresponding edges of the apertures of the half-cells opening downwards in the upper panel 2. The joining faces or edges are defined, in this case, by the straight lines CD, DE, EF and PC which are in a horizontal plane. These lines are the diagonals of the vertical faces CIDK, DJEL, ENFl-I and FGCM (see FIG. 1). The elementary panels of half-cells, 1 and 2, each comprise half-cells opening upwards and other half-cells opening downwards which are placed back to back and have common walls. As can clearly be seen in FIG. 2, in each elementary panel of half-cells, l or 2, there exist four neighbouring halfcells 11 to 14, which open upwards and which surround or define by their faces or side walls a half-cell 21 which opens downwards and vice versa. Thus, the lower corners B of the four half-cells, 11 to 14, define the square aperture of the lower half-cell 21, whilst the junction D of the apertures of the upper half-cells, 11 to 14, coincides, save for the thickness of the walls, with the top A of the half-cell 21 which opens downwards. In order to make FIG. 2 clearer, only the halfcells 11 and 21 have been shown in full-lines. The halfcell 21 defined by the corners C, D E, F, G, H,

K, L and A corresponds to the upper half-cell C, D, E, F, G, H, K, L, A of FIG. 1, whilst the lower half-cell C, D, E, F, I, J, M, N, B of FIG. 1 corresponds to the half-cells 11 to 14 of FIG. 2. A face, for example DIBJ, of the half-cell coincides with or forms the face AGF'I-l of the half-cell 21, and so on.

An arrangement of three elementary panels comprising half-cells opening upwards and downwards as in FIGS. 2 and 3 is shown, in perspective, in FIG. 4. The panels are aligned for superposition, the joining plane shown in dotted lines between the three panels 31, 32 and 33 being parallel to the plane CDI of the half-cell 11 according to FIG. 2. If these three elementary panels are joined together, for example, by gluing, along the edges surrounding the apertures a cellular flotation structure according to the invention is produced with rhombododecahedral cells formed between panels 31 and 32, and 32 and 33, while the upper panel 31 defines half-cells opening upwards and the lower panel 33 defines half-cells opening downwards.

Given that the side walls of the half-cells 11 to 14 and 21 of an elementary panel 1, 2, 31, 32 or 33 of the Figures discussed include only walls which are perpendicular to the plane defined by the apertures and walls which diverge from the bottom of the half-cells towards the apertures, it is easily understood that these panels of half-cells can be unitarily produced by moulding, for example, by injection into a mould comprising two parts, the projecting parts of which define the shapes of the half-cells and leave spaces between them which correspond to the walls of the half-cells.

In FIG. 5, a cross-sectional plane is shown which is perpendicular to the straight line passing through two three edge comers, as shown corners H and I, and through the centre of a regular rhombododecahedron, which gives a plane of cross-section of the dodecahedral cell, in the shape of a regular hexagon OPQRST dividing the cell into upper and lower half-cells.

FIG. 6 shows an elementary panel 1 comprising a plurality of lower half-cells of FIG. 5 which open upwards, this being an elementary panel on which a second upper elementary panel 2 of upper half-cells of FIG. 5 and opening downwards can be superposed, with the hexagonal apertures abutting as at OPQRSTO, in FIG. 5. Whole rhombododecahedral cells are thus produced, as defined by the corners A to N of FIG. 5.

. In this case also, the elementary panels of half-cells '1 and 2, can be moulded separately by means of a moulding process, for example, by injection] If the cross-sectional plane 0 to T defining the apertures of half'cells is a horizontal plane, all the edges passing through the top of the hexagon O to T, such as the edges DL, KA, CG and the like are vertical. It follows that the body of a moulded half-cell of this type can easily be removed from a mould of the appropriate shape.

As all the faces of a regular rhombododecahedron are identical and in pairs which are parallel to one another, the elementary panels of half-cells 1 and 2 can also be joined, for example by gluing at the faces of their closed bottoms. This can be seen in FIG. 7, wherein a single half-cell 71 which is imagined to belong to an elementary panel of half-cells opening upwards, rests with each of its three bottom faces 72, 73 and 74 in contact with a face of one of three half-cells 75, 76 and 77 which are adjacent to one another and open downwards, and each'of which has a common side wall or face with the other. In order to make FIG. 7 clearer, the half-cell 77 is shown incomplete. It will be noted that the planes of the upwardly and the downwardly opening apertures are parallel.

Another embodiment of elementary panel consists of two superimposed layers of such half-cells, all opening either upwards or downwards which have side walls perpendicular to the planes of the apertures. Each side wall is common to two half-cells, and each half-cell has three bottom walls common to half-cells opening in the opposite direction. The bottom walls are inclined, not vertical, to the planes of the apertures.

FIG. 8 shows three superimposable elementary panels 81, 82 and 83 each comprising both a layer of halfcells opening upwards 84, and a layer of half-cells opening downwards 85. Each of the half-cells which open upwards, for example 86, of the upper layer 84, is surrounded by six identical half'cells, 86 86 86 86,, 86 and 86 and has six'side walls 87,, 87 87 87,, 87 and 87 which are perpendicular to the plane of the apertures of the half-cells. Each side wall is common to two adjacent half-cells. The half-cells of the lower layer 85, which open downwards, have the same arrangement as the half-cells of the upper layer 84, but are displaced laterally relative to them in such a way that each half-cell of the lower layer has one interior wall in common with each of the three half-cells of the upper layer 84 and vice versa. Thus, as can be seen in FIG. 8, with respect to the elementary panel 82, three 7 adjacent upwardly opening half-cells, for example, 86, 86., and 86 each have three bottom walls, one wall 88,, 88 and 88 from each half-cell is also one of the three bottom walls of the downwardly opening half-cell 88. In order to make the drawing clearer, the upper-halfcell 86, has been cut along a vertical. plane passing through a vertical frontal wall of the upper half-cell 86 and of the lower half-cell 88; of the three bottom walls 88,, 88 and 88 only the'wall 88 is shown in full lines;

, With this construction also, the moulding of the elementary panels 81 to 83 is very easy. In order to form a cellular flotation structure, it suffices to glue or to weld the edges of the half-cells of at least three superimposed elementary panels together, thereby producing two layers of complete cells of rhombododecahedral shape.

In FIG. 9 a cross-sectional plane is shown in a regular rhombododecahedron which is perpendicular to and bisects a straight line passing through the centre of the dodecahedron and through the centres U and V of two of its faces, as shown in AFGI-l and BDIJ. Two halfcellsare thus obtained, havirigapertures with edges, shown in partby a broken line, in the shape'of an. irregularhexagomthe sides of which coincide, either with edges or with the diagonals of faces of the rhorribododecahedron. In FIG. 9, the irregular hexagon is defined bythecorners CKLENMCBy reason of the particular arrangement of-lthe cross-sectional plane CKLENMC, the two faces'AFGH and DBU'are'parallel to the said cross-sectional plane. Aseach of the walls of a half-cell is parallel-to one of the walls of the complementary half-cell it is again possible to produce elementary panels of half-cells'nof which some open up wards and the others open downwards;

Such apanel can be seen inFIG. 10, in which half- 8 on the two panels will abut in parallel relationship. Thus, the marginal zones 113 ,113 113;, and the like, of the half-cells 113 opening downwards in the upper panel 111 can be joined by gluing to the corresponding edges, 114,, 114 114 and the like, of the half-cells 114 opening upwards in the lower panel, the two halfcells 113 and 114 thus forming a whole and leaktight cell of rhombododecahedral shape. I

The half-cells lls'opening upwards on the upper panel 111 and the half-cells 1 16 opening downwards on the lower panel 112, can be joined and glued to one another by their bottom or top walls 115,, and 116 It is also possible to do away with the bottom or top walls of the half cells of one of the two elementary panels 11 1 and 112, so that the bottom or top walls of the halfcells of one elementary panel are formed by the bottom walls of the half-cells of the adjacent elementary panel.

The cellular flotation structure of the invention suitably comprise. at leastthree elementary panels of halfcells, which, whenthey are glued together, form two 3 same side,feither upwards or downwards, can be filled,

cells such as 90v open upwards and are surrounded by downwards, for example 94, is surrounded by four halfcells opening upwards, 90,95, 97 and 98, and by two half-cells opening downwards, 93 and 99. Thus, with the exception of the bottom'or top wall, the side walls, such as 90,, 90 ,90 90,, 90 and 90,,, are common ad jacent half-cells such as 91 to 96. The top'walls, for example 94, of the half-cells opening downwards are parallel to the upwardly opening apertures such as 90 and vice versa. A

The elementary panel of half-cells shown in FIG. 10 is defined onboth sides by' parallel planes including apertures and the bottom or top walls of the half-cells; The elementary panel of halfcells such as that shown in FIG. 10 can easily be manufactured by means of a moulding process by'injection, making use of two halfmoulds having projections in the shape of the appropriate semi-rhombododecahedra. r '5 Heat.-curable synthetic materials can be used as the moulding material forall the embodiments .described above. 1

FIG. 11 shows two elementary panels of half-cells, 111 and 112, each identical to the elementary panel of half-cells shown in FIG. 10. The upperpanel 111 is arranged above the lower panel 112, such that the apertures of the half-cells of the upper panel 111 can be positioned over the apertures of the half-cells ofthe lower panel, and that the closed inner walls of thehalf-cells afterv moulding, with a synthetic material. FIG. 12 shows an elementary. panel with a double layer of halfcells of the type according to FIGS. 7 and 8, but with the outwardly. and upwardly opening half-cells 120 filled or packed. as. at-121 after' the moulding ofthe panel, with aheat-curable.andrigidsynthetic material 123, preferably of the same nature as that of the material forming the .walls of the panel, s o that the finished cellular flotation structure has noempty outside halfcells. 4

7 As can be seen in FIG. 13, it is also possible to produce the outside elementary panels 131 and 132 of the cellular flotation structure in such a way that they comprise only half-ells 133 which all open on the same face of the panel, and thatthe other face, that.i s to say the outsideface'135, of the panel is continuous. Such a panel is obtained directlyduring the moulding of this outside elementary. panel of half-cells. In this case, there is not necessary so much material above the actual half-cells as to make this panel as'thick as a normal panel with adouble layer of half-cells 137. The panel can be'thicker orv less thick than such a panel.

FIG." 13 shows a first, upper, marginal panel "131, an intermediate panel with a double layer 137 and a sec- 0nd, lower, marginal panel 132. The upper panel 131 has a plane continuous upper faceon the outer side of the flotation structure and, on the inner side of the paneL'several half-cells" 133 which all open downwards,

' towards the inside of the volume. The'intermediate panel 137 has a double layer of half-cells such as is shown in FIGS. 7and 8 and comprisesome opening upwards and some downwards. The lower marginal panel 132 is made in exactly the same way as the upper marginal panel 13l,except that its half-cells 141 all open,

ries of whole cells of rhornbododecahedral' shape. a I

It is easy to understand that the cellular flotation structure can include any number of intermediate elementary panels. It is obvious that the gluing of two adjacent elementary panels must be perfectly leaktight in order that each whole cell is isolated from the others.

The marginal panels of the embodiments shown in FIGS. 4 and 11 can be produced in a manner analogous to that described in connection with FIGS. 12 and 13.

The thickness of the walls and the dimensions of the cells can be adjusted to the needs of each case. However, it has been found that a good resistance to implosion and a good degree of buoyancy is obtained if the thickness of the walls is of the order of one-tenth of the diameter of the sphere which envelopes the rhombododecahedral cells.

I claim:

1. A buoyant cellular structure for deep immersion in water having a high resistance to implosion relative to the overall density thereof when immersed, comprising a plurality of water-tight cells of identical hollow rhombododecahedral shape and arranged in juxtaposed relation, each wall of juxtaposed cells constituting a common' wall there-between to eliminate 7 intermediate voids, said cells beingarranged in at least two superposed layers, each of said cells being formed of two semi-cells, each in the form of a semirhombododecahedron having free edges surrounding an aperture, a pair of said semi-cells being joined together along their free edges to form a cell, said free edges and apertures lying in median planes of said cells, a plurality of semi-cells being arranged as panels in which the apertures of said semi-cells face outwardly on at least one of said panels and a plurality of said panels are assembled in stacked relation, each of the semicells on the at least one surface of one panel forming with each facing semi-cell of an adjacent panel, a layer of water-tight cells, the common walls of said cells having a thickness between about one/twentieth and about one/fourth of the diameter of the rhombododecahedral cells. I

2. A structure as claimed in claim 1 wherein at least one of said panels has two opposed parallel faces and comprises a layer of said semi-cells, some of said semicells having their apertures facing outwardly on one parallel face and the remaining semi-cells having their apertures facing outwardly on the other parallel face of said panel. 1

3. A structure as claimed in claim 2 wherein the distance between said opposed parallel faces of said panels is equal to the height of said semi-cells perpendicular to said faces.

4. A structure as claimed in claim 3 wherein each of said semi-cells includes an interior corner opposite to its aperture and each parallel face of said panels comprises the apertures of some of said semi-cells and the interior corners of the remaining semi-cells.

5.,A structure as claimed in claim 4 wherein said apertures lie in median planes of the rhombododecahedra formed by said semi-cells, and said rhombododecahe- -dra have edges and opposed corners at which four of said edges meet, said median planes being perpendicular to lines joining two opposed corners.

6. A structure as claimed in claim 3 wherein each semi-cell includes an inner bottom wall parallel to the opposed aperture thereof, and wherein each opposed parallel face of said panels comprises apertures of some of saidsemi-cells and the bottom walls of the remaining semi-cells.

7. A structure as claimed in claim 6 wherein the apertures of said semi-cells lie in median planes of the rhombododecahedra formed by said semi-cells, and said rhombododecahedra have opposed parallel walls, said median planes being perpendicular to a line joining the mid-points of two opposed parallel walls.

8. A structure as claimed in claim 1 wherein the apertures of a single layer of said semi-cells lie in a single face of each of said panels, each semi-cell having walls perpendicular to said single face.

9. A structure as claimed in claim 1 wherein at least one of said panels has two opposed parallel faces and comprises a first and a second super-posed layer of said semi-cells the apertures of said first layer of semi-cells facing outwardly from one parallel face and the apertures of said second layer'of semi-cells facing outwardly from the other parallel face.

10. A structure as claimed in claim 9 wherein each of said semi-cells includes walls perpendicular to said opposed parallel faces and inclined inner walls, each inclined inner wall of one semi-cell being common to the inclined inner walls of a superposed semi-cell.

11. A structureas claimed in claim 9 wherein the apertures of said semi-cells lie in median planes of the rhombododecahedra formed by said semi-cells, and said rhombododecahedra have edges and corners opposite to said apertures at which three of said edges meet.

12. A structure as claimed in claim 1 wherein said panels are moulded from a plastic material.

13. A structure as claimed in claim 1 wherein said panels have marginal cells with outside walls and said outside marginal walls are reinforced. 

1. A buoyant cellular structure for deep immersion in water having a high resistance to implosion relative to the overall density thereof when immersed, comprising a plurality of watertight cells of identical hollow rhombododecahedral shape and arranged in juxtaposed relation, each wall of juxtaposed cells constituting a common wall there-between to eliminate intermediate voids, said cells being arranged in at least two superposed layers, each of said cells being formed of two semicells, each in the form of a semi-rhombododecahedron having free edges surrounding an aperture, a pair of said semi-cells being joined together along their free edges to form a cell, said free edges and apertures lying in median planes of said cells, a plurality of semi-cells being arranged as panels in which the apertures of said semi-cells face outwardly on at least one of said panels and a plurality of said panels are assembled in stacked relation, each of the semi-cells on the at least one surface of one panel forming with each facing semi-cell of an adjacent panel, a layer of water-tight cells, the common walls of said cells having a thickness between about one/twentieth and about one/fourth of the diameter of the rhombododecahedral cells.
 2. A structure as claimed in claim 1 wherein at least one of said panels has two opposed parallel faces and comprises a layer of said semi-cells, some of said semi-cells having their apertures facing outwardly on one parallel face and the remaining semi-cells having their apertures facing outwardly on the other parallel face of said panel.
 3. A structure as claimed in claim 2 wherein the distance between said opposed parallel faces of said panels is equal to the height of said semi-cells perpendicular to said faces.
 4. A structure as claimed in claim 3 wherein each of said semi-cells includes an interior corner opposite to its aperture and each parallel face of said panels comprises the apertures of some of said semi-cells and the interior corners of tHe remaining semi-cells.
 5. A structure as claimed in claim 4 wherein said apertures lie in median planes of the rhombododecahedra formed by said semi-cells, and said rhombododecahedra have edges and opposed corners at which four of said edges meet, said median planes being perpendicular to lines joining two opposed corners.
 6. A structure as claimed in claim 3 wherein each semi-cell includes an inner bottom wall parallel to the opposed aperture thereof, and wherein each opposed parallel face of said panels comprises apertures of some of said semi-cells and the bottom walls of the remaining semi-cells.
 7. A structure as claimed in claim 6 wherein the apertures of said semi-cells lie in median planes of the rhombododecahedra formed by said semi-cells, and said rhombododecahedra have opposed parallel walls, said median planes being perpendicular to a line joining the mid-points of two opposed parallel walls.
 8. A structure as claimed in claim 1 wherein the apertures of a single layer of said semi-cells lie in a single face of each of said panels, each semi-cell having walls perpendicular to said single face.
 9. A structure as claimed in claim 1 wherein at least one of said panels has two opposed parallel faces and comprises a first and a second super-posed layer of said semi-cells the apertures of said first layer of semi-cells facing outwardly from one parallel face and the apertures of said second layer of semi-cells facing outwardly from the other parallel face.
 10. A structure as claimed in claim 9 wherein each of said semi-cells includes walls perpendicular to said opposed parallel faces and inclined inner walls, each inclined inner wall of one semi-cell being common to the inclined inner walls of a superposed semi-cell.
 11. A structure as claimed in claim 9 wherein the apertures of said semi-cells lie in median planes of the rhombododecahedra formed by said semi-cells, and said rhombododecahedra have edges and corners opposite to said apertures at which three of said edges meet.
 12. A structure as claimed in claim 1 wherein said panels are moulded from a plastic material.
 13. A structure as claimed in claim 1 wherein said panels have marginal cells with outside walls and said outside marginal walls are reinforced. 